i agree with all that you have said, appart from your last statement. and it wasn't an idea that was criticized or mocked, it was a person, a being, the prophet of the muslims. he is not an idea, he is a person and it is/was a personal attack on the person.
A few things to make note of:
1. This is not a living person we're talking about, and it cannot reasonably be said that he has any feelings that might be hurt.
2. Even if he was considered to be alive, he would be what we call a 'public persona', meaning that he would have to expect a certain amount of attention, not all of it positive. This is no different than when newspapers publish cartoons and caricatures of politicians and celebrities.
3. Him being a prophet, while factual, is an idea on the level that it is an idea that you can even have prophets in the first place.
Thus, according to 1. while it might be in bad taste, no-one's feelings is directly being hurt.
According to 2. public persona just has to suck it up at times. This might seem unfair, especially if the person in question did not seek the status of celebrity, but I don't see this changing any time soon.
And finally, 3. the reason he is famous in the first place, and the reason anyone at all is getting upset, is because of an idea, a religion, thus bringing us full circle back to my original argument.
At this point I would also like to make a personal note regarding these caricatures.
When they were first published my initial though was
"that was a bit unnecessary". While I would never question anyone's right to free speech, I didn't, at the time, see any reason for what seemed like blatant insults.
This, however, changed when I saw the reactions of certain groups of Muslims around the world, their response being one of violence and destruction of property. At that point I thought
"we need this, because we need these people to grow a thicker skin, and to learn to respect the freedom of speech".
So, in fact, the responses given from certain groups of Muslims actually changed my stance from one of moderate distaste for the caricatures to a rather extreme disgust for the Muslims in question.